Process for the agglomeration of fine iron ores



Patented Mar. 30, 1937 A UNITED STATES rnoonss more THE AGGLOIKEBATION FINE IRON (IRES Eugen Kugener, Neunkirchen/Saar, Germany No Drawing. Application 72,659. In Germany April 3, 1936, Serial No.

December I, 193? ,2 Claims. (01. 75-5) The charging of blast furnaces with fine iron ores' is unprofitable and accompaniedby great technical dimculties. It is therefore necessary to convert such ore by agglomeration or sintering into lump form suitable for smelting in blast furnaces. A considerable proportion of the cost of this agglomeration is represented by the fuel consumption. If poor fine ores'are dealt with,

these can only be converted into lump form profitably by using a very cheap fuel, but of course the material has nevertheless to satisfy stringent demands as to compressive strength and porosity. Now, there is obtained in the coal washing and cleaning plants of collieries and metallurgical works, in addition to the coal andthe waste, the so-called middle quality or product, that is coal containing a large proportion of waste or shale.

This middle product which economically is-al-' most useless as fuel or for the recovery of byproducts, might be used as a suitable fuel addition in the agglomeration into lump form, in particular of poor fine ores, since highgrade fuels are not required in this agglomeration process.- It should, however, be borne in mind, that even for this purpose, the fuel must be of a definite particle size. Consequently, the middle quality material which is obtained in different particle sizes, would have to be previously crushed. In the course of this crushing, a great deal of clay containing particles, will be freed. n the charge for the agglomerating installation is then produced from the crushed middle quality and the fineore with the addition of the necessary water, the result is a thick loamypaste which can hardly be'moved out of the mixing bunkers. In addition, during the sintering operation the middle quality material gives off volatile substances which stop up the fans and pipes. It would therefore be necessary to work ata higher temperahim than is required for the sintering in order to prevent a premature condensation of these substances. Here,,again, the danger arises of the agglomerates commencing to'fuse and losing their porodty.

These diflculties in the use of the middle quality coal as fuel addition for agglomerating fine iron ores into lump form are obviated according to this inv'entionby the middle quality coal being used in the coked conditio The. coke obtained inthiswayiseasilyreducedinsizeandmaybe brought to the desired particle size without the production of dust. The coke is very porous and fairly strong. It takes up the fine ores in its pores as and forms. in consequence of its uniformly distributed inorganic constituents n skeleton or framework in forming the pieces, which framework ensures with very little formation of dust, the bearing strength of the agglomerates durin smelting.

The high content of ash in this coke forms a desirable addition in sintering, since it is fairly uniformly distributed and acts as a consolidating fiux without impairing the porosity of the agglomerates. At the points, where the ash comes into contact with the sintering material, a cementingtakes place in a very short time without, however, .the pores of the adjacent particles being closed up.

During treatmentin the blast furnace also, the uniform distribution of the ash content of the coke is of advantage for the formation of slag;

A further advantage of this coke is to be seen in that the carbon is distributed over the ash framework in a comparatively thin uniform layer. The coke is consequently adapted to ignite easily, so that the sintering takes place with a comparatively small addition of fuel, whereby ahigher production is ensured. It is furthermore of importance that the iron content of the agglomerate increases in an astonishing manner as'compared .with the rawore.

Finally, the fuel gas temperature can be kept at least 20 to 30 C. lower, and this lower temperature means that working can take place more rapidly and the output of the sintering installation increased.

It is further of advantage that in the coking of I the middle quality coal, the entire-,by-products and-gases can be recovered and utilized, whereas otherwise-theypass partly unused into the fiues' in the different firing operations.

Example Coal 'niiddlings are cokedfin the customary manner in a coke oven. The by-products are recovered. The thus produced coke isdisintegrated v and care should be taken that practically no dust is The fine iron oreis then, mixed with the coke particles in a suitable mixing equipment, for instance, mixers which are used in foundries and for sand mixing. The addition 'of coke amounts to between 9% to 12% according to the percentage of ash in the coal. These .figures ,may,

of'cou'rsle, be underor overrated in special cases. Thenthe necessary amount of water of between 12% to' 15% is added. The mixture is brought on a Dwight-Lloyd sintering machine with a suction areaoi'42sq.m. Thetimeofsinteringisabout 10 minutes and the height of the charge is about 320 mm. The sintering temperature is maintained at between 1,050 and 1,100 C. The

amount of air, which is drawn through the .ore comprising coking the so-called coal middlings charge, amounts to 3,000 in? per minute. A vacuum of 1,000 mm. water column is used. The products agglomerated are rigid bodies, which are very resistant against mechanical stresses.

What I claim is: I 1. The process of treating finely divided iron ore comprising coking the so-called coal middlings recovered in coal washing plants, disintegrating the thus produced coke. mixing the coke particles with the fine ore and sintering the mixture on a sintering machine at an adequate temperature to form rigid agglomeratesQ 2. The process of treating finely divided iron recovered in coal washing plants, disintegrating the thus produced coke to form fine particles without generating dust, mixing'the coal particles with the fine ore and sintering the mixture on a sintering machine at an adequate temperature 10 to form rigid agglomerates.

EUGEN xuonmm. 

